Anyone with a five-year-old can tell you that sharing is not a completely ingrained behavior in humans. Sure, we’re a very social species that owes a lot to getting along with each other, but that doesn’t seem to translate into immediately sharing our own resources with others. So if sharing can feel uncomfortable enough that a kid might turn down a free chocolate chip cookie just to avoid giving half to his sister, how did humans ever really get started teaching our children that this was a behavior worth practicing? It may seem like this question is now impossibly tangled up in economic, social and even marketing influences, but researchers believe a system used by the nomadic Hadza people of East Africa may offer some insight into how cultures developed standards about sharing.

The Hadza don’t have some single, perfect formula for dividing up resources, because they don’t live in permanent groups. Instead, individuals are likely to move between various camps on a regular basis, each with its own expectations for how people conduct themselves. So while one person may have a predisposition to share or withhold food they’ve gathered, this seems to be overruled by the expectations of whichever camp that individual is living in at the time. From the perspective of my uncooperative five-year-old, this would mean that even if he didn’t want to split a cookie, that preference wouldn’t matter as much as what his current camp expected of him.

Who holds their honey sticks?

Rather than relying on self-reported generosity, researchers tested these standards for sharing over the course of six years across 56 different camps. During that time, 383 people participated, although 137 ended up participating more than once because they had switched camps in the same order as the researchers. The test itself tried to simplify sharing by turning it into a game that asked people to hold or share some of the four straws of honey each participant was issued. Any straws shared with the group pool at the end of the game would be matched three-times over, with that resulting windfall being shared equally among all participants. So in theory, everyone could end up with 12 sticks of honey if they all pitched in, although knowing that didn’t mean that every participant really maximized their gains.

Some camps just tended to hold on to their own straws more than others. What’s more, participants that had played in a previous camp generally changed their sharing strategy to match how their new peers were sharing, rather than donating the amount they’d done in the previous camp. This strongly suggests that social expectations outweigh personal preferences, which has likely helped societies overcome individuals instincts to protect their own resources. If this holds true for all humans, I guess my household has been stingier around my five-year-old than I’d like to admit. If we’d really like to bring out his generosity, we need to make sure the whole family is willing to share our cookies before asking him to do so.